CARBOHYDRATES

Presented by;

M Pharm (Pharmaceutical Chemistry) students

Gunturu .Aparna

Akshintala. Sree Gayatri

Thota. Madhu latha

Kamre. Sunil

Daram. Sekhar

University college of pharmaceutical sciences

Department of pharmaceutical chemistry

Acharya Nagarjuna University

Guntur

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Cells of organisms - plants, fungi, bacteria.

Insects, animals - produce a large variety oforganic compounds.

Many substances were obtained anciently, e.g.foodstuffs, building materials, dyes, medicinals, andother extracts from nature.

Oils & Fats, Terpenoids

Prostaglandins Alkaloids,

Vitamins Flavanoids

Steroids Carbohydrates

Lignins lignans

Proteins Nucleic acid

Antibiotics pigments

EXAMPLES OF NATURAL PRODUCTS

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CARBOHYDRATES

Carbohydrates are the most abundant organic compounds in

the plant world.

They act as storehouses of chemical energy (glucose, starch,

glycogen); are the components of supportive structures in plants

(cellulose), crustacean shells (chitin) and connective tissues in

animals (acidic polysaccharides) and are essential components of

nucleic acids (D-ribose and 2-deoxy-D-ribose).

Carbohydrates make up about three fourths of the dry weight of

plants.

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Simple Sugars

Monosaccharides

Disaccharides

Complex Carbohydrates

Starch

Glycogen

Cellulose (a form of fiber)

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A. Structure and Nomenclature

The general formula CnH2nOn

with one of the carbons being the carbonyl group of either an

aldehyde or a ketone.

The most common monosaccharides have three to eight carbon

atoms.

The suffix-ose indicates that a molecule is a carbohydrate, and

the prefixes tri-, tetr-, pent-, and so forth indicate the number of

carbon atoms in the chain.

Monosaccharide containing an aldehyde group are classified

as aldoses; those containing a ketone group are classified as

ketoses.

A ketose can also be indicated with the suffix ulose; thus, a

five- carbon ketose is also termed a Pentulose.

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Another type of classification scheme is based on the

hydrolysis of certain carbohydrates to simpler

carbohydrates i.e. classifications based on number of

sugar units in total chain.

Monosaccharides: single sugar unit

Disaccharides: two sugar units

Oligosaccharides: 3 to 10 sugar units

Polysaccharides: more than 10 units

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Sucrose (C12H22O11) + H2O acid or certain enzyme Glucose (C6H12O6) + Fructose (C6H12O6)

MonosaccharidesDisaccharides

There are only two trioses: the aldotriose glyceraldehyde and the

ketotriose dihydroxyacetone

Glyceraldehyde

(an aldotriose)

CHO

CHOH

CH2OH

CH2OH

C

CH2OH

O

Didroxyacetone

(a ketotriose)

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We will consider the stereochemistry of carbohydrates by focusing largely on the aldoses with six or fewer carbons.

The aldo hexoses have four asymmetric carbons and therefore exist as 24 or 16 possible stereo isomers.

These can be divided into two enantiomeric sets of eight diastereomers.

HOH2C

OH

HC

OH

HC

OH

HC

HC

OH

CH

O

Aldohexoses

four asymmetric carbons

24 = 16 stereoisomers

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Similarly, there are two enantiomeric sets of four

diastereomers (eight stereoisomers total) in the aldopentose

series. Each diastereomer is a different carbohydrate with

different properties, known by a different name.

The aldoses with six or fewer carbons are given as Fischer

projections. Be sure you understand how to draw and interpret

Fischer projections, as they are widely used in carbohydrate

chemistry.

Each of the monosaccharides has an enantiomer. For

example, the two enantiomers of glucose have the following

structures: HC

OHH

HHO

OHH

OHH

CH2OH

HC

HO H

H OH

HO H

HO H

CH2OH

O

Enantiomers of glucose

D - L -

O

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It is important to specify the enantiomers of

carbohydrates in a simple way.

Suppose you had a model of one of these glucose

enantiomers in your hand. You could, of course, use

the R,S system to describe the configuration of one

or more of the asymmetric carbon atoms.

A different system, however, was in use long before

the R,S system was established.

The D,L system, which came from proposals made

in 1906 by M. A. Rosanoff, is used for this purpose.

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Glyceraldehydes contains a chiral center and therefore exists

as a pair of enantiomers.

Glyceraldehyde is a common name; the IUPAC name for this

monosaccharide is 2,3-dihydroxypropanal.

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Chemists commonly use two-dimensional representations called Fischer projections to show the configuration of carbohydrates.

Following is an illustration of how a three-dimensional representation is converted to a Fischer projection.

CHO

CH OH

CH2OH

CHO

C HHO

CH2OH

(R)-Glyceraldehyde (S)-Glyceraldehyde

4 C3

1

2

4 C2

1

3

(S) (R)

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CHO

HO H

H OH

H OH

CH2OH

CHO

H OH

HO H

H OH

CH2OH

CHO

HO H

HO H

H OH

CH2OH

CHO

H OH

H OH

H OH

CH2OH

D-(-)-ribose

(2R,3R,4R)

D-(-)-arabinose

(2S,3R,4R)

D-(+)-xylose

(2R,3S,4R)

D-(-)-lyxose

(2S,3S,4R)

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CHO

H OH

H OH

CH2OH

CHO

HO H

H OH

CH2OH

D-(-)-Erythrose D-(-)-Threose

CHO

H OH

H OH

H OH

CH2OH

D-(-)-Ribose

H

OH

O

OH

H2

CHO

H

O

OH

H2

CHO

OH

H

OH

O

OH

CH2

OH

HO4

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2(R),3(R),4(R),5-tetrahydroxypentanal

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Even though the R,S system is widely accepted today as a

standard for designating configuration, the configuration of

carbohydrates as well as those of amino acids and many other

compounds in biochemistry is commonly designated by the D,L

system proposed by Emil Fischer in 1891.

At that time, it was known that one enantiomer of glyceraldehyde

has a specific rotation of + 13.5; the other has a specific rotation of

-13.5.

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Fischer proposed that these enantiomers be

designated D and L (for dextro and levorotatory) but

he had no experimental way to determine which

enantiomer has which specific rotation.

Fischer, therefore, did the only possible thing-he

made an arbitrary assignment.

He assigned the dextrorotatory enantiomer an

arbitrary configuration and named it D-

glyceraldehyde. He named its enantiomer L-

glyceraldehyde.

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Fischer could have been wrong, but by a stroke of good

fortune he was correct, as proven in 1952 by a special

application of X-ray crystallography.

D- and L-glyceraldehyde serve as reference points for the

assignment of relative configuration to all other aldoses and

ketoses.

CHO

CH OH

CH2OH

D-Glyceraldehyde

[]D = +13.5

CHO

C HHO

CH2OH

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L-Glyceraldehyde

[]D = -13.525

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The reference point is the chiral center farthest from

the carbonyl group. Because this chiral center is

always the next to the last carbon on the chain, it is

called the penultimate carbon.

A D-monosaccharide has the same configuration at

its penultimate carbon as D-glyceraldehyde (its-OH

is on the right when written as a Fischer projection);

an L-monosaccharide has the same configuration at its penultimate carbon as L-glyceraldehyde.

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CHO

CH OH

CH2OH

*

D-Glyceraldehyde

CHO

H OH

H OH*

CH2OH

CHO

HO H

H OH*

CH2OH

D-Erythrose D-Threose

CHO

H OH

H OH

H OH*

CH2OH

CHO

HO H

H OH

H OH*

CH2OH

CHO

H OH

HO H

H OH*

CH2OH

CHO

HO H

HO H

H OH*

CH2OH

D-Ribose D-Arabinose D-Xylose D-Lyxose

CHO

OHH

OHH

OHH

OH*H

CH2OH

CHO

HHO

OHH

OHH

OH*H

CH2OH

CHO

OHH

HHO

OHH

OH*H

CH2OH

CHO

HHO

HHO

OHH

OH*H

CH2OH

CHO

OHH

OHH

HHO

OH*H

CH2OH

CHO

HHO

OHH

HHO

OH*H

CH2OH

CHO

OHH

HHO

HHO

OH*H

CH2OH CHO

H OH*

H OH

H OH

HO H

CH2O

H

D-Allose D-Altrose D-Glucose D-Mannose D-Gulose D-TaloseD-GalactoseD-Idose

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Three main disaccharides: sucrosemaltose lactose

All are isomers with molecular formula C12H22O11

On hydrolysis they yield 2 monosaccharide. which soluble in water Even though they are soluble in water, they

are too large to pass through the cell membrane.

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Is a sugar used at home

Also known as the cane sugar

When hydrolyzed, it forms a mixture of glucose and fructose

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Commonly known as malt sugar.

Present in germinating grain.

Produced commercially by hydrolysis of starch.

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Commercially known as milk sugar.

Bacteria cause fermentation of lactose forming lactic acid.

When these reaction occur ,it changes the taste to a sour one.

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Sucrose and maltose will ferment when yeast is added because yeast contains the enzyme sucrase and maltase.

Lactose will not ferment because yeast does not contain lactase.

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The chemical reactions of these sugars can be used to distinguish them in the laboratory.

If you have 2 test tubes containing a disaccharide, C12H22O11.

To determine if it is sucrose lactose or maltose.

We can use the alkaline Cu complex reaction of glucose and the principle of fermentation.

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Polysaccharides are large molecules containing 10 or more monosaccharide units. Carbohydrate units are connected in one continuous chain or the chain can be branched.

1. Storage polysaccharides contain only -

glucose units. Three important ones are

starch, glycogen, and amylopectin.

2. Structural polysaccharides contain only -

glucose units. Two important ones are

cellulose and chitin. Chitin contains a modified -glucose unit

Polysaccharides

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Amylose and amylopectin—starch

Starch is a mixture of amylose and amylopectin and is

found in plant foods.

Amylose makes up 20% of plant starch and is made

up of 250–4000 D-glucose units bonded α(1→4) in a

continuous chain.

Long chains of amylose tend to coil.

Amylopectin makes up 80% of plant starch and is

made up of D-glucose units connected by α(1→4)

glycosidic bonds.

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Glycogen is a storage polysaccharide found in

animals.

Glycogen is stored in the liver and muscles.

Its structure is identical to amylopectin, except that

α(1→6) branching occurs about every

12 glucose units.

When glucose is needed, glycogen is hydrolyzed in

the liver to glucose.

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Structural Polysaccharides

Cellulose

Cellulose contains glucose units bonded (1→4).

This glycosidic bond configuration changes the

three-dimensional shape of cellulose compared with

that of amylose.

The chain of glucose units is straight. This allows

chains to align next to each other to form a strong

rigid structure.

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Cellulose is an insoluble fiber in our diet because we lack the enzyme cellulase to hydrolyze the (1→4) glycosidic bond.

Whole grains are a good source of cellulose.

Cellulose is important in our diet because it assists with digestive movement in the small and large intestine.

Some animals and insects can digest cellulose because they contain bacteria that produce cellulase.

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Chitin

Chitin makes up the exoskeleton of insects

and crustaceans and cell walls of some fungi.

It is made up of N-acetyl glucosamine

containing (1→4) glycosidic bonds.

It is structurally strong.

Chitin is used as surgical thread that

biodegrades as a wound heals.

It serves as a protection from water in insects.

Chitin is also used to waterproof paper, and in cosmetics and lotions to retain moisture.

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Heparin:

Heparin is a medically important

polysaccharide because it prevents clotting in the

bloodstream.

It is a highly ionic polysaccharide of repeating

disaccharide units of an oxidized monosaccharide

and D-glucosamine. Heparin also contains sulfate

groups that are negatively charged.

It belongs to a group of polysaccharides called

glycosaminoglycans.

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